Which of the following is the main difference between TCP and UDP?

A.
TCP data flows in two directions, while UDP data flows from server to client.

B.
The TCP header implements flags, while the UDP header does not.

C.
The TCP header implements checksum, while the UDP header does not.

D.
TCP connections can be secured by stateful firewalls, while UDP connections cannot.

Explanation:
Transmission Control Protocol (TCP) is a connection-oriented transport protocol. Connection-oriented transport
protocols provide reliable transport. When a computer wants to send data to another computer, TCP will first
establish a connection between the two computers. When a sending computer sends data segments, the
receiving computer acknowledges receipt of the segments. If the receiving computer does not receive an
expected segment, the sending computer will send it again.
User Datagram Protocol (UDP) is a connectionless transport protocol. Connectionless transport protocols
provide unreliable transport. With UDP, there is no connection establishment between the sending and
receiving computers. If a data segment is lost in transit, the sending computer will not know about it so it will not
resend the segment.
TCP uses control messages to manage the process of contact and communication. TCP uses a set of control
flags in the TCP header to indicate whether a segment is being used for control purposes or just to carry data.